Method for obtaining a fuel from jatropha seeds that are fich in fat

ABSTRACT

A method for obtaining a fuel from  jatropha  seeds having a fat content of at least 30% by weight, and simultaneously obtaining a protein-rich meal.

This application is a national stage of International Application PCT/EP2011/073109, filed Dec. 16, 2011, and claims benefit of and priority to German Patent Application No. 10 2010 055 419.7, filed Dec. 21, 2010, the content of which Applications are incorporated by reference herein.

BACKGROUND AND SUMMARY

The present invention relates to a method for obtaining a fuel from jatropha seeds having a fat content of at least 30% by weight and simultaneously obtaining a protein-rich meal.

Getting oil from fat-rich seeds is conventional. Methods currently used are mainly the following:

-   1. Pressing plus hexane estraction -   2. 2-Stage pressing -   3. Cold pressing

Fuels are obtained using mainly methods 1 and 2 above, to maximize oil yield. With neither method is the seed dehulled before oil recovery, and so the husks remain in the de-oiled meal and thus adversely affect the nutritional value. Oil quality with these high-yield methods is relatively low, necessitating costly and complex refining steps to allow this oil to be used as biofuel.

EP 0 267 933 A1 discloses a process for obtaining vegetable oil, in which at least one reagent for reducing the phospholipid content is added to the oil-containing material. Plants such as, for example, soybeans or maize are cleaned, dried and dehulled in preparatory steps. Those plant parts can then be ground. Here, for example, oil is additionally added. In the extraction of vegetable oil from these soybeans or maize, hydrochloric acid, among other things, is also employed. This is used to reduce the phospholipid content.

A hydrophobic phospholipid is converted into a hydratable species. However, because the hydration of phospholipids is reversible, chelating agents, precipitating agents or the like must additionally be used in order to stabilize the phospholipids in the aqueous solution.

GB 1 179 584 A discloses a process for obtaining fats. The aqueous extraction of animal fats was therein optimized by extracting such a fat in a pH range of from 4.1 to 5.8. That pH value can be achieved, among other things, by addition of acids, for example hydrochloric acid, sulfuric acid, citric acid or acetic acid.

WO 98/53698 A1 and EP 1 905 309 A1 disclose the processing of rapeseeds, soybeans, maize and sunflower seeds. These are first ground. Solids are then removed. Finally, washing of the oil phase is carried out, it being possible to establish a pH value of from 2 to 10 during washing, by addition of Tris-HCl. Formulation to an emulsion is then carried out. This emulsion is used in the foodstuffs sector and in the feeds sector, but also in connection with pharmaceutical and cosmetic products.

GB 1 402 769 A discloses a process for obtaining oil by an enzymatic process. Following the enzymatic treatment, which is carried out at pH values from pH=3 to pH=6, decomposition of the cell walls of the oil-containing plant product takes place with liberation of the oil within from 2 to 24 hours.

EP 2 163 159 A1 discloses the production of oil from rapeseed.

After preparation and dehulling of the rapeseed, pressing of the rapeseed is carried out, in which a press cake and rapeseed oil are formed. In a process step known as “degumming”, the rapeseed oil is freed of phospholipids, which agglomerate in a reaction tank. This is followed by a process step of drying and esterification.

Biodiesel and crude glycerol are separated by transesterification in the process.

In further subsequent steps, proteins and various other reusable materials can be obtained from the different fractions of the rapeseed oil or of the rapeseed press cake. The process described here has only limited suitability for the production of fuels, because the oil yield from the pressing of dehulled rapeseed is very low. Owing to the high residual fat content in the de-oiled press cake, the latter can be utilized to only a limited degree.

In the use of fuels from oil plants, oil from jatropha seeds, also called purging nuts, has been found to be a valuable alternative, because jatropha oil has a higher cetane number compared with rapeseed oil, for example, and because the jatropha plant also grows in nutrient-poor soils.

Besides oil, proteins are an essential constituent of jatropha seed. However, the high husk component of the seeds is problematic at up to 40 percent by weight. If said husk component is not removed prior to the de-oiling, a protein-rich, meal with a low oil content is difficult to obtain.

Today's methods primarily use pressing of the seeds. In order to achieve a high yield, an appreciable husk content in the product is essential.

Embodiments according to the present disclosure provide a method with which a useful fuel can be obtained to a great extent from these plant seeds or nuts.

Such an embodiment or embodiments are discussed below.

A method, according to the embodiment of the present disclosure, for obtaining a fuel from fat-containing jatropha seeds, having a fat content of at least 30% by weight, or, for example, at least 40% by weight, comprises the following method steps:

-   a. removal of husk components; -   b. comminution of plant seeds or nuts; -   c. addition of water and/or acid to the comminuted plant seeds or     nuts, to form an oil-containing suspension; and -   d. separation of the crude oil from the suspension;

The pH value of the suspension prior to the separation of crude oil is, for example: pH≦3.5.

The crude oil obtained here is an intermediate in the production of a fuel. It contains a proportion of residual water and optionally also smaller solid particles of the plant seed.

The method just described according to the present disclosure for obtaining a fuel from fat-containing jatropha seeds additionally comprises the following method steps:

-   e) oil polishing; -   f) neutralization; and -   g) drying of the oil.

Oil polishing is a method of cleaning the oil. The crude oil is processed further by use of filtration technology or separation technology and is cleaned of or separated from solids residues and water. The solids content of the polished crude oil is reduced to the extent that this oil can be used as a fuel. The residual water content in the fuel is lowered, for example, to 0.1% by weight or less by drying.

The solid phase obtained here is suitable as an intermediate in the production of a protein-rich meal.

The oil thus obtained is extremely low in phosphates, magnesium and calcium and complies with the standard for biofuels, that is DIN 51605 when polished without further processing. Unlike pressed oils, complex refining of oils can thus be avoided.

Water and acid can be fed separately to the suspension or can be mixed to form a dilute acid before being added to the suspension. In such a case, the dilute acid already has an appropriate concentration prior to the addition in order to adjust the pH value of the suspension to ≦3.5.

In the production of fuel from jatropha seeds having a fat content of at least or more than 30% by weight, or, for example, at least or more than 40% by weight, it has been found, surprisingly, that the yield of crude oil increases significantly at a pH value of ≦3.5.

According to embodiments of the present disclosure, fuel, and if appropriate, also simultaneously a protein-rich meal is/are obtained from jatropha seeds, that is, the purging nuts of the jatropha plant.

Embodiments of the method according to the present disclosure are discussed herein and in the appended claims.

Although a significant increase in the yield of fuel is already to be observed at a pH value of ≦3.5 as compared with processing at neutral pH, a particularly advantageous increase in the yield can, however, be achieved with a suspension having a pH value ≦3.2.

A further increase in the yield of fuel can be achieved by carrying out the adjustment of the pH value of the suspension specifically by use of hydrochloric acid. Crude oil can be liberated from the comminuted plant seeds or nuts as extensively as possible with a dwell time of at least 30 minutes, or, for example, from 30 to 60 minutes, after addition of the acid. Because a higher temperature facilitates the liberation of the crude oil from the plant seeds or nuts, it is, for example, advantageous for a temperature of from 60 to 80° C., or, for example, from 80 to 95° C., to be established in the product with the added water.

The plant seeds can be cleaned before being comminuted, in order thus to remove foreign matter adhering to the plants. In addition, the proportion of solids and foreign substances in the suspension can be reduced before comminution by prior dehulling and drying.

Alternatively or in addition, according to the present disclosure, the yield of fuel can be increased by carrying out the comminution of the plant seeds or nuts by use of a mill having a fine degree of grinding. As a result of the finer degree of grinding of the plant seeds or nuts, less crude oil is retained inside the solid components.

The separation of the crude oil can, within the scope of the present disclosure, take place from the suspension by repeated de-oiling. After a first de-oiling, the suspension, with a content of crude oil of 4 percent or less, is introduced into a second decanter or returned to the decanter of the first de-oiling for further de-oiling of the suspension.

Washing of the crude oil in order to obtain the fuel can, for example, advantageously be carried out in a centrifuge, or, for example, in a separator.

Other aspects of the present disclosure will become apparent from the following descriptions when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows, schematically, a plant for obtaining a fuel from jatropha seeds, in accordance with the present disclosure.

FIG. 1 a shows a plant for obtaining a meal, in accordance with the present disclosure.

FIG. 2 shows a diagram illustrating the dependence of the oil content in the de-oiled suspension at different pH values, in accordance with the present disclosure.

FIG. 3 shows a diagram illustrating the dependence of the oil content in the de-oiled suspension with use of different acids, in accordance with the present disclosure.

FIG. 4 shows a diagram illustrating the dependence of the oil content in the de-oiled suspension with different dwell times, in accordance with the present disclosure.

DETAILED DESCRIPTION

FIG. 1 shows, schematically, a plant with which, in an embodiment of the present disclosure, jatropha seeds A are processed into a crude jatropha oil D which is suitable as a fuel. The jatropha seeds, or nuts A, having, for example, previously been cleaned and dehulled.

In a first step of the treatment, the jatropha seeds A are first transferred to a mill 1 for comminution. The nuts A are here broken up and comminuted in a grinder. This grinding process can, within the scope of the present disclosure, be additionally facilitated by the supply of further oil.

The fragments of the comminuted jatropha seeds have a specific mean grain size, which is specified by the grinder. This can be carried out in slotted mills, for example.

Before being comminuted, the jatropha seeds A may, for example, be dehulled and/or dried. These preparatory steps facilitate the comminution, or grinding, of the jatropha seeds A. At the same time, the protein content is increased significantly by removal of the husk components.

The embodiments according to the present disclosure include an important advantage over conventional methods used today, because the husk fraction can now be used separately, and the protein content of the de-oiled meal permits its use in various ways.

It is within the scope of the present disclosure that more than 50%, or, for example, more than 80%, or, for example, all of the husk components are removed.

After grinding, the comminuted jatropha seeds are transferred in the form of an oil/solid mixture to a buffer tank 2. From there, they are transported by way of a first eccentric screw pump 3 to a mixer or mixing station 4.

In the mixing station 4, hot water and acid, for example, hydrochloric acid, HCl, are fed to the ground product and mixed in such a manner that the suspension has an elevated temperature of from 60 to 80° C., or, for example, from 80 to 95° C.

During this introduction of hot water and acid, a suspension of solids, oil and water having a pH value of ≦3.5 is formed.

In order to increase the yield of fuel and to obtain a meal having a low oil content, it is very important that the suspension formed has a pH value of ≦3.5.

The hot water and the acid, for example, concentrated hydrochloric acid, can also be introduced separately into the mixing station and form a suspension having a pH value of ≦3.5 by intensive stirring. Although this sequence of method steps may not be preferred, because a locally high concentration of acid is formed in the suspension, it can be used as an alternative, in accordance with the present disclosure, to the addition of a dilute acid to form a suspension.

In a further embodiment according to the present disclosure, that may be less preferred, a different acid, for example sulfuric acid or citric acid, can also be used instead of hydrochloric acid to adjust the pH value.

The suspension is then, for example, transferred to a dwell container 5. It has been found, surprisingly, that the crude oil yield can, for example, advantageously additionally be increased in the course of a dwell time. Sedimentation is prevented by gentle stirring and thus improves the yield. To that end, the dwell container 5 has a stirrer 6. The dwell time in the dwell container 5 can, for example, be from 30 to 60 minutes. Depending on the crude material and the acid used, the crude oil yield can even fall slightly again with a longer dwell time.

From the dwell container 5, the suspension is transported by way of a second eccentric screw pump 7 to a decanter 8. This decanter 8 can, for example, be in the form of a two-phase separating decanter, where the first phase comprises de-oiled suspension having a residual oil content of less than 6% by weight, based on the content of solids in the suspension, and the second phase comprises crude vegetable oil and, optionally, solid particles, dissolved in a disperse manner, and residual water.

Alternatively to a two-phase separating decanter, and within the scope of the present disclosure, the de-oiling can be carried out in a 3-phase decanter or in a combination of a clarifying decanter and a subsequent 3-phase separator.

The crude vegetable oil is collected in a container, or buffer tank, 9 and transferred by way of a third eccentric screw pump 10 and by way of a heat exchanger 11, for example, a plate heat exchanger, to a centrifuge 12. Disposed between the heat exchanger 11 and the centrifuge 12 there is a feed for hot water. This water, for example, advantageously has a temperature of from 60 to 80° C., or, for example, from 80 to 95° C. The centrifuge 12 may be, for example, in the form of a three-phase separator, and in the separator both a separation of the water and oil phase and a clarification of the oil and water phases, removing solid particles, take place.

There is discharged from the centrifuge 12 a clear oil phase in the form of jatropha oil D, which can be processed further by neutralization and drying to give a product that is suitable for use as a fuel in combustion engines.

Furthermore, following the oil polishing, the residual water content of the oil phase can be lowered to a residual water content of about 0.05% or less by vacuum drying (not shown. The content of free fatty acid can be reduced by the neutralization. An important step in the optimization for obtaining oil from jatropha seeds A is the optimization of the adjustment of the pH value to ≦3.5.

A further advantageous increase in the yield, in accordance with the present disclosure, is achieved by the choice of a suitable acid, the dwell time, the ratio of crude oil and water and/or acid in the suspension, and the fine adjustment of the pH value.

FIG. 2 shows, in a diagram in accordance with the present disclosure, measured values of the residual oil content in de-oiled suspensions at different pH values, which suspensions were discharged from centrifuge 8. A lower residual oil content is significant for a better yield of jatropha oil and a higher protein content in the meal. A high residual oil content in the suspension accordingly reduces the yield of jatropha oil D obtained and lowers the protein content in the meal.

The temperature of the suspension was always 90° C., the dwell times in the dwell container were always 60 minutes, and the ratio of water to solid/oil mixture was always 1:1. The tests at pH=3 were carried out with hydrochloric acid. In the case of the suspension at pH=5.5, citric acid was used to adjust the pH value.

The different residual oil contents of the measured values depicted in the diagram do not show significant differences in the residual oil content at pH values between 5.5-6.5 and the residual oil content of an aqueous extraction in the neutral pH range. At a pH value of 3.0, however, a significant reduction in the residual oil content to 3.6% is to be observed. As is clear from the diagram at FIG. 2, an increase in the yield of jatropha oil is, surprisingly, noted when the pH value is lowered to below 3.0.

In addition to the important factor of the pH value, the use of different acids also leads to varyingly high yields of jatropha oil D. In the diagram of FIG. 3, citric acid, hydrochloric acid and sulfuric acid in water were compared with one another under comparable measuring conditions. The temperatures of the suspension were always 90° C., the pH value of the solutions was always 3.0, the dwell times in the second buffer tank were always 60 minutes, and the ratio of water to the solid/oil mixture was always 1+1. It is clear from FIG. 3 that extraction using hot water with the addition of hydrochloric acid is preferred to sulfuric acid and citric acid, because a particularly large amount of jatropha oil can, in that case, be extracted from the solids of the suspension.

FIG. 4 shows a tendency concerning the dwell times of the suspension in the dwell container. These tests were carried out with addition of an aqueous citric acid solution at a pH value of 3.0. It can be seen that a dwell time of 30 minutes is sufficient to achieve the liberation of the oil phase from the suspension.

Too long a dwell time, for example, more than 60 minutes, in the dwell container leads to an increase in the residual oil content and accordingly to a reduction in the overall yield. The dependence on the dwell time is, however, also dependent at least in part on the acid used. The dwell time of from 30 to 60 minutes has thus been found to be particularly advantageous in the case of the use of HCl.

It has been found in tests, in accordance with the present disclosure, that an additional increase in the yield of fuel can be achieved if the ratio of water to product after the addition of water and acid is in the range of from 1:2 to 2:1.

The water content in the suspension, may, for example, be greater than 35% by weight, or, for example, be greater than 40% by weight.

It has been found, in accordance with the present disclosure, that a ratio of 1:1 between the solid/oil mixture and the aqueous phase, that is to say a water content of about 50% in the suspension, is particularly advantageous.

Aspects of embodiments of the method according to the present disclosure are discussed below.

Test 1:

800 g of jatropha seed, wild seed from Cape Verde, were broken manually by use of tongs. The husks were separated off manually. Breaking was carried out in such a manner that only a small amount of fines and dust formed.

The seed, husks and flesh were analyzed. The seed contained 91% dry matter, or, DM, which included 16% protein and 35.7% fat. The husk fraction of 298 g, or 37.7%, contained 91% DM, which included 3.3% protein and 0.4% fat.

The kernel fraction of 502 g, or 62.3%, contained 91% DM, which included 24.6% proteins and 56.5% fat.

The two fractions were separated in a visually pure manner, in each case merely with traces of the other fraction.

It is apparent in this respect that components of the jatropha seed that have a relatively low fat content are removed very effectively by manual dehulling.

Test 2:

1013 kg of jatropha seed, wild seed from Cape Verde, were dehulled by use of a test plant from Probat.

Breaking was carried out by use of a reflex breaker with a gap of 3 mm. The breaker was operated at 1300 rpm, the throughput was 308 kg/h, on average.

Separation of the husks was carried out in a pilot-scale air separator. The mean throughput was 296 kg/h.

The following fractions were obtained:

-   1. 507 kg of kernel fraction (50%) -   2. 494 kg of husk fraction (48.8%) -   3. 12 kg of dust fraction from the separating cyclone (1.2%)

The husk fraction contained 91.4% DM, which includes 7.3% proteins and 7.8% fat.

The kernel fraction contained 91.2% DM, which includes 19.8% proteins and 49.8% fat.

Both the kernel fraction and the husk fraction visually still contained components of the other fraction.

It is apparent in this respect that components of the jatropha seed that have only a relatively low fat content are also removed to a large degree by automated dehulling.

Test 3:

300 g of dehulled, ground jatropha seed were mixed in a glass beaker with 450 g of water and stirred for 60 minutes at 90° C. in a water bath. A pH value of 6.2 was established.

A further sample was adjusted to a pH value of 3.0 with 90 ml of HCl and likewise stirred for 60 minutes at 90° C. in a water bath.

The two samples were then centrifuged for 3 minutes at 4500×g in a heatable laboratory centrifuge.

The solids were then investigated for the residual fat content.

While the sample without pH adjustment had a residual fat content of 12.06%, based on DM, the residual oil content of the de-oiled sample with pH adjustment was only 3.6.

This shows the advantage of the pH value adjustment.

Test 4:

160 kg of water were heated indirectly to 95° C. in a heatable stirred vessel. 112 kg of dehulled, ground jatropha seed were then added. The suspension was adjusted to a pH value of 3.0 with 5.8 kg of concentrated hydrochloric acid, and the suspension was adjusted to a temperature of 90° C.

The suspension was stirred gently for 60 minutes in the vessel.

The suspension was then separated into an oil phase and a phase of de-oiled suspension in a CA 220-08-33 2-phase separating decanter from Westfalia Separator Group GmbH. The bowl speed was 4750 rpm and the differential speed was 18 rpm.

The feed rate was 300 l/h and was set by use of an adjustable eccentric screw pump.

The discharge rate of the oil phase was 63 l/h.

The de-oiled solid contained 34.8% DM, with 5.4% fat, based on dry matter DM.

Test 5:

180 kg of already de-oiled jatropha suspension with 34.8% DM and 5.4% fat, from test 4, in the dry matter DM were mixed in a stirred vessel with 50 liters of water.

The suspension was stirred gently for 30 minutes and during this was heated to 90° C. by use of an indirect heat supply.

The suspension was then separated into an oil phase and a phase of de-oiled suspension in a CA 220-08-33 2-phase separating decanter from Westfalia Separator Group GmbH. The bowl speed was 4750 rpm and the differential speed was 15 rpm.

The feed rate was 300 l/h and was set by use of an adjustable eccentric screw pump.

The discharge rate of the oil phase was 9 l/h.

The de-oiled solid contained 29.6% DM, with 3.9% fat, based on dry matter DM.

A comparison of examples 4 and 5 shows the advantage of forming the oil-containing suspension, in particular with prior separation of the husk constituents, as in test 4.

Test 6:

36 kg of jatropha oil so obtained were mixed in a stirred vessel with 1 liter of water and heated to 90° C. with an indirect heat supply.

The oil phase was then separated into an oil phase and an aqueous phase in a BTC 3-03-107 solid bowl centrifuge from Wesffalia Separator Group GmbH. Solids in the oil were collected in the bowl of the centrifuge and removed after the test.

The aqueous phase contained 2.0% DM and had a fat content of 0.05%.

The oil phase had the following parameters:

carbon residue: 0.45% (m/m); oxidized ash: <0.005% (m/m); phosphorus: <0.5 mg/kg; sodium: <0.5 mg/kg; magnesium: <0.5 mg/kg; calcium: <0.5 mg/kg; potassium: <0.5 mg/kg; aluminum: <0.5 mg/kg; iron: <0.5 mg/kg.

The very low phosphate and magnesium content of the oil phase is very important.

According to test 4, an oil phase is first obtained. The yield can be improved by repeated de-oiling. The de-oiling steps of tests 4, 5 and 6, each of which is optional and in accordance with the present disclosure, confirm this.

Although the present disclosure has been described and illustrated in detail, it is to be clearly understood that this is done by way of illustration and example only and is not to be taken by way of limitation. The scope of the present disclosure is to be limited only by the terms of the appended claims. 

We claim:
 1. A method for obtaining a fuel from jatropha seeds having a fat content of at least 30% by weight, and simultaneously obtaining a protein-rich meal, the method steps comprising: providing jatropha seeds; removing husk components from the seeds; comminuting the dehulled seeds; adding one or both of water and acid to the comminuted seeds to form an oil-containing suspension; separating crude oil from the suspension wherein the pH value of the suspension before separation of the crude oil is ≦3.5; oil polishing the crude oil; performing neutralization; and drying the crude oil.
 2. The method as claimed in claim 1, further comprising the step of de-oiling the protein-rich meal and drying of the de-oiled protein-rich meal.
 3. The method as claimed in claim 1, wherein the pH value of added water is ≦3.2.
 4. The method as claimed in claim 1, wherein the pH value of the suspension is adjusted with hydrochloric acid before separation of the crude oil.
 5. The method as claimed in claim 1, wherein water and acid are added, and a dwell time of at least 30 minutes is observed.
 6. The method as claimed in claim 1, wherein the separating of the using a decanter.
 7. The method as claimed in claim 1, wherein the oil-containing suspension has a temperature of from 60 to 80° C. before separation of the crude oil.
 8. The method as claimed in claim 1, wherein the oil-containing suspension has a temperature of from 80 to 95° C. before separation of the crude oil.
 9. The method as claimed in claim 3, wherein a water-to-product ratio is in the range of from 1:2 to 2:1.
 10. The method as claimed in claim 3, wherein the water content of the suspension is greater than 35% by weight based on the total mass of the suspension.
 11. The method as claimed in claim 1, further comprising the step of cleaning of the jatropha seeds occurs prior to the comminuting step.
 12. The method as claimed in claim 11, further comprising the step of drying of the plant jatropha seeds occurs after the cleaning step and before the comminuting step.
 13. The method as claimed in claim 1, wherein the separating of the crude oil occurs by repeating a de-oiling from the suspension.
 14. The method as claimed in claim 1, wherein after the separating of the crude oil from the suspension, the suspension has a residual oil content of less than 4% by weight, based on the total mass of solids in the suspension.
 15. The method as claimed in claim 1, wherein the oil polishing of the crude oil occurs in a separator.
 16. The method as claimed in claim 1, wherein the fat content is at least 40% by weight.
 17. The method as claimed in claim 1, wherein water and acid are added, and a dwell time of from 30 to 60 minutes is observed.
 18. The method as claimed in claim 5, wherein a water-to-product ratio is in the range of 1:2 to 2:1. 